Article dispensers having a variety of features are known in the art. By way of example, U.S. Pat. No. 4,875,599 discloses a battery-powered business card dispenser. When a button is pressed, a timer is used to operate a motor for a fixed time necessary to dispense a card.
U.S. Pat. No. 4,026,436 discloses a time controllable cigarette dispenser which automatically dispenses cigarettes at preset time intervals after a dispensed cigarette has been removed from a dispensing tray by a user.
In addition to various other articles, prior art dispensers are also capable of dispensing single sheets (such as coupons) from a stack of sheets. Again by way of example, U.S. Pat. No. 4,919,412 discloses a single sheet draw-off system including a draw-off roller coupled to a pressure sensor. Stack pressure is adjusted based on the time required to draw off a single sheet. A predetermined range of forces needed to draw a single sheet off the stack is taught. A pressure plate is moved along a toothed guide rail to adjust stack pressure.
U.S. Pat. No. 4,475,732 discloses a sheet feeding device which senses the stack force between a feed member and the stack. The stack force may be adjusted by rotating the feed member about a pivot point. U.S. Pat. No. 4,039,181 discloses a coupon dispenser for dispensing a coupon into an open package as it passes along on a conveyor. Photo diodes count coupons as they are dispensed.
U.S. Pat. No. 4,717,043 discloses a coupon dispenser for use with a vending machine. Single coupons are separated from the stack and moved to a ready position. Once money is deposited in the machine, coupons are moved from the ready position to a dispensing position where they are held by nip rollers. U.S. Pat. No. 3,899,841 discloses a coupon display and clip for attaching to grocery shelf edging.
A disadvantage of prior art dispensers for point of purchase promotions is that they are not designed for low power consumption and thus are not efficiently operable with an integral power supply such as batteries. A further disadvantage of prior art coupon dispensers is that they provide virtually no protection against excessive coupon removal or "loading" by a single customer.